This research project is concerned with the structure and the development of the nervous system. Special stains have been developed in this laboratory which are specific for nerve fibers and cells. These stains have a good histologic picture and all organ systems can be studied. A large collection of specially prepared serial sections of human embryos and fetuses is required. The growth of nerve fibers and the maturation and migration of certain nerve cells can be demonstrated at definite critical periods of development. This is true of the central and peripheral nervous systems. Our earlier studies have been concerned mainly with the development of the cranial and spinal nerves and their connections. At the present time we are concentrating our efforts on the nerves innervating the developing teeth. Other studies will include (1) the development of the brain and the conduction pathways of the central nervous system, (2) studies on the development of the cranial nerves, and (3) the growth, migration, and maturation of nerve fibers and cells. Better staining methods and research techniques make advances in these areas of research promising.